Federer sprints into US Open fourth round as Nadal battles 'nerves' to advance

After two marathons, Roger Federer had the after-burners on, sprinting past Feliciano Lopez 6-3, 6-3, 7-5 and into the fourth round of the US Open on Saturday after Rafael Nadal recovered from a set down to advance and move a step closer to a semi-final showdown between the two great rivals.

Chasing a sixth US Open title, Federer needed just one hour and 46 minutes under a closed roof at Arthur Ashe Stadium to put away the 31st seed Lopez, leaving plenty in the tank after being forced to go the distance in his opening two matches.

"It was clearly nice to go up two sets to love for a change," Federer said. "I was happy I had good energy because I think that was my biggest worry, that somehow after the two five-setters that I was going to feel a little slow, hard to throw the engine on, that I would have to force myself so much, I would get tired from that.

"It didn't happen. I'm really pleased with the performance. It's exactly I guess maybe what I needed going into the next round."

Next up for the 36-year-old Swiss is  a fourth round meeting with German Philipp Kohlschreiber, who made light work of Australian John Millman.

"I know Philipp very well. Practised with him a ton," Federer said. "Had some good matches against him in the past. He's a good player. Got great rotation on the ball. Plays with a lot of topspin. Has a nice one-handed backhand, which I love to see, of course."

Nadal's progress wasn't quite as serene, but after dropping the opening set in a tie-break to Leonardo Mayer, the Spanish world No 1 upped the ante to defeat his Argentine opponent 6-7, 6-3, 6-1, 6-4.

Nadal needed to wait for his 14th opportunity to break his opponent but by that time Mayer had taken the first set by winning the tiebreak.

"Of course, you are under stress when you see that you have opportunities almost in every game, and you are not able to convert them," Nadal said. "At the beginning you get nerves when you don't convert opportunities."

Once he broke to lead 3-2 in the second set, Nadal appeared to be free of his early jitters and took hold of the match.

"When finally I did it, everything changed. I was able to play more freely, to start to attack better with my forehand," said the Spaniard, who hit only 13 unforced errors in the last three sets, having made 13 in the opening set.

"I had more forehands down the line, hitting some good backhands later. I think the level of tennis after that break have been very positive."